Extensive red scaly rashes like this are often misdiagnosed
as a form of dermatitis and treated with a strong topical steroid cream.
Initially this seems to work. The redness goes and the scale is less prominent
but as soon as the cream is ceased the rash returns, more irritable than ever.
The scale takes longer to reform and the rash covers a bigger area than before!
This sequence of events should make you think you are dealing with a tinea
corporis infection. If the old adage of always taking a skin scraping for
microscopy and culture of all red scaly rashes had been followed at the outset,
before prescribing the topical steroid, then the diagnosis would have been made
much earlier. This patient was predisposed to a tinea infection by being on
Methotrexate for rheumatoid arthritis but the situation is also seen in
diabetics or patients on oral steroids or other immunosuppressing drugs or
conditions. Patients usually start with fungus in the groin or between the toes
and by scratching these areas transfer fungus to other areas of the body. He
grew Trichophyton rubrum, a very common anthropophilic fungus which often
presents just with scale and redness and very little inflammation. It is
usually picked up from another human being . Fungi acquired from animals elicit
a more marked inflammatory reaction. He was treated with oral terbinafine 250
mgs daily for 6 weeks.
